Hektoen Enteric Agar
Approximate Formula* Per Liter
Proteose Peptone ..................................................... 12.0 g
Yeast Extract .............................................................. 3.0 g
Bile Salts No. 3 ........................................................... 9.0 g
Lactose ..................................................................... 12.0 g
Saccharose ............................................................... 12.0 g
Salicin ........................................................................ 2.0 g
Sodium Chloride ........................................................ 5.0 g
Sodium Thiosulfate .................................................... 5.0 g
Ferric Ammonium Citrate ........................................... 1.5 g
Agar ......................................................................... 14.0 g
Bromthymol Blue ..................................................... 65.0 mg
Acid Fuchsin ............................................................... 0.1 g
Brilliant green bile agar is both selective and differential. It is selective for enteric bacteria, particularly Salmonella and Shigella, by inhibiting the growth of gram-positive bacteria and non-enteric gram-negative bacteria due to the presence of brilliant green dye and bile salts. It is also differential because it allows for the differentiation of enteric bacteria based on their ability to ferment carbohydrates, resulting in color changes in the medium.
Mycobacterium phlei is a non-fastidious organism that is commonly found in soil and water. It is not commonly grown on Eosin Methylene Blue (EMB) agar, as EMB agar is more selective for gram-negative enteric bacteria. Instead, Mycobacterium phlei is typically cultured on media specifically designed for mycobacteria, such as Middlebrook agar or Lowenstein-Jensen agar.
Eikenella corrodens generally does not grow on MacConkey agar because it is a fastidious organism that requires enriched media for growth. MacConkey agar is selective for gram-negative bacteria and primarily supports the growth of enteric bacteria, which Eikenella is not. Instead, Eikenella grows well on blood agar or other enriched media that provide the necessary nutrients.
The melting point of agar is useful because it determines the temperature at which agar solidifies and forms a gel. This property makes agar an important ingredient in microbiology labs for culturing bacteria and other microorganisms. By solidifying at a specific temperature, agar provides a solid medium for microbial growth and isolation.
Bile salts in MacConkey agar inhibit the growth of Gram-positive bacteria by disrupting their cell membranes. This selective property allows for the preferential growth of Gram-negative bacteria on MacConkey agar, making it a useful medium for the isolation and differentiation of enteric bacteria.
Yes. Serratia is a Gram negative rod from the Enterobacteriaceae family. The Hektoen Enteric agar allows the growth of Gram negative bacteria while inhibiting growth of Gram positive bacteria.
MacConkey agar: Selective for Gram-negative bacteria, inhibits the growth of Gram-positive bacteria. Hektoen enteric agar: Selective for Gram-negative enteric pathogens, such as Salmonella and Shigella species. Thiosulfate-citrate-bile salts-sucrose (TCBS) agar: Selective for Vibrio species, especially Vibrio cholerae. Cefsulodin-irgasan-novobiocin (CIN) agar: Selective for Yersinia species.
PEA agar, also referred to as Phenylethyl Alcohol Agar is a medium used by microbiologists to grow microorganisms. The ingredient that supplies nitrogen is casein.
Campylobacter jejuni will not grow on MacConkey agar because it is a selective and differential medium designed to support the growth of Gram-negative enteric bacteria while inhibiting the growth of Gram-positive bacteria. Campylobacter jejuni is a Gram-negative bacterium, but it is not an enteric bacterium, so it lacks the specific enzymes needed to utilize the nutrients in MacConkey agar for growth.
The conclusion drawn if no growth appeared on MacConkey agar and EMB agar after inoculation of the media and an incubation period could be the bacteria used was possibly a Gram positive non-enteric sample.
mannitol is a type of sugar, so it supplies the carbon in the MSA medium
Mycobacterium phlei is a non-fastidious organism that is commonly found in soil and water. It is not commonly grown on Eosin Methylene Blue (EMB) agar, as EMB agar is more selective for gram-negative enteric bacteria. Instead, Mycobacterium phlei is typically cultured on media specifically designed for mycobacteria, such as Middlebrook agar or Lowenstein-Jensen agar.
Agar is produced by the cell walls of some species algae. It is derived from an all natural chemical and ingredient called Gelidium amansi.
Agar agar is a common vegan substitute for gelatin. It is a plant-based ingredient derived from seaweed that can be used in place of gelatin in recipes.
The melting point of agar is useful because it determines the temperature at which agar solidifies and forms a gel. This property makes agar an important ingredient in microbiology labs for culturing bacteria and other microorganisms. By solidifying at a specific temperature, agar provides a solid medium for microbial growth and isolation.
mannitol is a type of sugar, so it supplies the carbon in the MSA medium
Bile salts in MacConkey agar inhibit the growth of Gram-positive bacteria by disrupting their cell membranes. This selective property allows for the preferential growth of Gram-negative bacteria on MacConkey agar, making it a useful medium for the isolation and differentiation of enteric bacteria.